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January 2018
Slate Crossfit Journal Club
Karny Jacoby, MD FPMRS

EFFECTS OF PROLOGNED SITTING
With the publication of the meta analysis in Annals of Internal Medicine looking at the relationship of risk of disease incidence and sedentary time, a new way to look at our lifestyles was introduced. We now have the “sitting is the new hypertension” mantra floating around. Lets look at the original article that ushered in this new concept and some other recent publications…
The paper below references the original article that is often cited by the press and by the standing desk manufacturers to get you to purchase. It is a meta-analysis of 47 articles that met the eligibility criteria on outcomes for cardiovascular disease, diabetes, cancer, and all-cause mortality. In the majority of studies, sedentary times were self-reported, which is a weakness in some of the articles. The gist of the analysis was that “hazard ratios associated with sedentary time and outcomes were generally more pronounced at lower levels of physical activity than at higher levels”. The conclusion was that despite the limitations of the study, that there was the marked heterogeneity in research designs, “prolonged sedentary time was independently associated with deleterious health outcomes regardless of physical activity. This sounds scary so lets look at some newer data…

Sedentary Time and Its Association With Risk for Disease Incidence, Mortality, and Hospitalization in Adults: A Systematic Review and Meta-analysis
Aviroop Biswas, BSc; Paul I. Oh, MD, MSc; Guy E. Faulkner, PhD; Ravi R. Bajaj, MD; Michael A. Silver, BSc; Marc S. Mitchell, MSc; David A. Alter, MD, PhD
Published: Ann Intern Med. 2015;162(2):123-132.

I thought this paper was nicely nuanced in that is stratified how the more frail you are, the more important exercise and reducing sedentary lifestyle is. What they found was that if you are NOT frail, neither exercise nor sedentary lifestyle made a difference in mortality. In other words, for young healthy folks, you can abuse your body for a while until it catches up to you! The deal is that exercise is a habit born of years and its best to get started early in your life…see last months blog for all the positive benefits!

CMAJ. 2017 Aug 21;189(33):E1056-E1064. doi: 10.1503/cmaj.161034.
Association between sedentary time and mortality across levels of frailty.
Theou O1, Blodgett JM2, Godin J2, Rockwood K2.
Author information
Abstract
BACKGROUND:
Sedentary behaviours are associated with adverse health outcomes in middle-aged and older adults, even among those who exercise. We examined whether the degree of frailty affects the association between sedentary behaviours and higher risk of mortality.
METHODS:
In this prospective cohort study, we used data from 3141 community-dwelling adults 50 years of age or older from the 2003/04 and 2005/06 cohorts of the US National Health and Nutrition Examination Survey. Time engaged in sedentary behaviours was measured using uniaxial accelerometers, and frailty was based on a 46-item frailty index. Mortality data were linked up to 2011. We used Cox proportional hazard models to estimate the hazard ratio (HR) of sedentary behaviour.
RESULTS:
We found that for people with low levels of frailty (frailty index score ≤ 0.1), sedentary time was not predictive of mortality, regardless of physical activity level (adjusted HR 0.90, 95% confidence interval [CI] 0.70-1.15). Among people who were vulnerable (0.1 < frailty index score ≤ 0.2) or frail (frailty index score > 0.2), sedentary time was associated with higher mortality only among those who were physically inactive (not meeting the criterion for moderate physical activity) (HR 1.16, 95% CI 1.02-1.33 for the group defined by 0.1 < frailty index score ≤ 0.2; HR 1.27, 95% CI 1.11-1.46 for the group defined by 0.2 < frailty index score ≤ 0.3; HR 1.34, 95% CI 1.19-1.50 for frailty index score > 0.3).
INTERPRETATION:
The effect of sedentary behaviours on mortality varied by level of frailty. Adults with the highest frailty level experienced the greatest adverse impact. Low frailty levels (frailty index score ≤ 0.1) seemed to eliminate the increased risk of mortality associated with prolonged sitting, even among people who did not meet recommended physical activity guidelines.
© 2017 Canadian Medical Association or its licensors.
In the article below, what we see is the added association of quality sleep to the mix of exercise and good diet…

Front Physiol. 2017 Nov 8;8:865. doi: 10.3389/fphys.2017.00865. eCollection 2017.
Improving Cardiometabolic Health with Diet, Physical Activity, and Breaking Up Sitting: What about Sleep?
Vincent GE1, Jay SM1, Sargent C1, Vandelanotte C1, Ridgers ND2, Ferguson SA1.
Author information
Abstract
Cardiometabolic disease poses a serious health and economic burden worldwide and its prevalence is predicted to increase. Prolongedsitting, lack of physical activity, poor diet, and short sleep duration are ubiquitous behaviors in modern society, and all are independent risk factors in the development of cardiometabolic disease. Existing evidence demonstrates that breaking up prolonged periods of sittingis beneficial for cardiometabolic health, however, studies have not controlled for prior sleep duration. This article examines how prolonged sitting and short sleep duration independently contribute to cardiometabolic risk, and how breaking up sitting and obtaining adequate sleep may reduce this risk. We suggest that as prolonged sitting and short sleep duration influence the same cardiometabolic parameters, there is potential for short sleep to attenuate the positive impact of breaking up prolonged sitting with physical activity. Likewise, breaking up prolonged sitting and obtaining adequate sleep together could improve predictors of cardiometabolic disease, i.e., the combined effect may be stronger than either alone. To explore these perspectives, we propose a research agenda to investigate the relationship between breaking up prolonged sitting with physical activity and short sleep duration. This will provide an evidence-base for informing the design of interventions to reduce the burden of cardiometabolic disease on communities worldwide.
KEYWORDS:
exercise; physical activity; sedentary behavior; sitting breaks; sleep restriction

In conclusion, it looks like a steady exercise program starting from at least before middle age (when is that anyway??) combined with healthy eating and good sleep hygiene will reduce your cardiovascular risk and all cause mortality…so, Slate Crossfitters, lets have a great new year and do some WOD’s together!

Karny